An infusion pump infuses fluids, such as medications or nutrients, into a patient's body. Infusion pumps administer an injection every minute, or injections when requested by the patient. An infusion schedule typically consists of periods of desired flow during which the motor driving the pump is energized, and periods when the desired flow rate is zero. During zero flow periods, the motor driving the pump is de-energized. De-energizing the motor when the flow rate is zero saves energy, a particularly beneficial feature when the infusion pump is operating on battery power.
Many infusion pumps use a peristaltic type pump where a roller assembly moves a roller to progressively compress a tube through which the fluid flows. When the motor is de-energized, it is undesirable for the roller assembly to rotate backward as this may siphon blood out of the patient. Normally, the stiction of the roller assembly and related motor are sufficient to prevent reverse rotation of the pump. However, some infusion methods, subcutaneous for example or other conditions, such as a pinched tube, may produce relatively high pressures, pressures sufficient to rotate the roller assembly in backward. Various mechanical mechanisms that prevent reverse pump rotation such as pawls and clutches are known. However if the pawl gets stuck, or the clutch does not engage, the roller assembly may rotate backward. Infusion pumps used on human patients are certified to have no single point of failures. That is, no single cause of failure should cause the pump to silently fail to operate correctly. Mechanical devices are not well suited for detecting a failure such as reverse rotation and reporting that a failure has occurred.
What is desired is a way to detect reverse rotation of an infusion pump, and make energy efficient use of a motor to prevent reverse rotation. It is further desired that if reverse rotation is detected, an indicator is activated.